Bioreduction of toxic hexavalent chromium by novel indigenous microbe Brevibacillus agri isolated from tannery wastewater

The present study is focused on the microbial bioreduction of hexavalent chromium generated from tannery waste. For the study, the treated and untreated tannery effluents were collected from an unexplored site of Manpura, Macheri, Jaipur (India). A few bacterial strains capable of tolerating and reducing hexavalent chromium were isolated, and the most capable one that reduced 85% of hexavalent chromium was identified to be Brevibacillus agri by 16S rDNA gene sequencing. This isolate could tolerate high concentrations of chromium up to 850 mg/l of potassium dichromate and showed maximum reduction of about 85% for 100 mg/l of hexavalent chromium at temperature 37 °C and pH 7.0 in 48 h. The potential of the partially purified enzyme to reduce hexavalent chromium was measured by diphenyl carbazide assay. Purified enzyme showed 0.26 units bioactivity to reduce Cr, in the presence of reduced nicotinamide adenine dinucleotide and K and V were observed to be 1.9 mM and 0.045 mM/min (mg protein), respectively. The current study, therefore, showed Brevibacillus agri capable of reducing hexavalent chromium without usage of toxic chemicals and, henceforth, prevented generation of harmful by-products.